Accurate sensing of intracranial electrical activity, for the purpose of determining epileptogenic foci or otherwise, typically requires use of a plurality of brain contacts. Epileptogenic mapping is one example of the use of electrical devices with plural-contact tissue-engagement members. Broadly speaking, there are two different kinds of intracranial electrical contact devices--depth probes and flexible flat surface members.
Depth probes, which are often referred to as "depth electrodes," penetrate deep into the brain tissue. On the other hand, flexible flat surface members, including what are sometimes referred to as "strip" electrodes and "grid" electrodes, are placed subdurally in direct contact with brain tissue at the surface of the brain.
Each of these different kinds of intracranial tissue-engagement members has a plurality of electrodes which are separated from one another by a non-conductive material on which the electrodes are mounted. Separate thin insulated lead wires extend from the tissue-engagement member for each electrode. Such lead wires extend away from the tissue-engagement member to means for connecting the lead wires with individual conductors, which lead to monitoring or recording equipment.
For each type of intracranial tissue-engagement member used in the prior art, the procedures for placement and hookup are of great importance. It is essential that the tissue-engagement members be inserted with a high degree of accuracy in order to avoid damage and in order that placement be in the most advantageous positions. It is also important that the flat flexible member be in proper contact with brain tissue for advantageous results. It is also essential that the lead wires extending from the tissue-engagement member be properly connected and that the fragile lead wires remain functional, without any breakage or disconnection.
While there has been much progress in the field of electrical brain-contact devices in recent years, existing devices and procedures have a number of problems and drawbacks. One significant problem is that the surgical placement and set-up procedures preceding the period of use are far too time-consuming and complex. Such procedures in some cases also lead to specific problems.
Such problems can be described best by generally describing at least certain parts of the placement and set-up procedures, as used, for example, in preparing for an extended period of epileptogenic sensing using grid or strip electrodes as the tissue-engagement members:
One of the early steps in existing placement and set-up procedures for grid and strip electrodes is making an incision in t he scalp over the site of proposed electrode placement. Then a burr hole is drilled in the skull or a skull area otherwise removed. One or more incisions are then made in the dura to accommodate placement of a grid or insertion of a strip. Dural tack-up sutures are placed in both dural margins.
The grid or strip electrode device is then placed or inserted, with the electrodes in contact with the brain tissue. When strip electrodes are used, a plurality of strips are usually inserted in each burr hole. The strips and grids may have a large number of electrical contacts. With grid electrodes, the number of contacts may be particularly high. After the grid or strips have been positioned, the dural edges are approximated with a suture.
The lead wires, which extend from the proximal end of each strip or grid, are passed through the sutured dura incision. All the wires, one for each electrode on the grid or on every strip, are then brought out through the skin by passing them through a needle and then drawing them through the scalp at a distance (usually 4-5 cm) from the skull opening. When there are numerous wires it is often necessary to tunnel in a number of directions through the scalp to sites spaced from the skull opening. This can be both very time-consuming and very hard on the patient's head.
When such wires have exited the scalp at the chosen sites, it then remains necessary to make electrical hookups of each of such wires in the appropriate manner. This is itself a time-consuming operation, and one in which there is a risk of incorrect hookups. The extended time required for such hookups is a problem in itself. And, the fragile lead wires are quite susceptible to breakage during these manipulative operations; if this occurs, it may be necessary to reopen the dura to remove and replace the grid or strip from which the lead wire broke and repeat many of the procedures described above.
In order to minimize the likelihood of lead wire breakage, lead wires of greater size may be used. However, increasing the diameter of the lead wires tends to increase the overall thickness of the strip or grid. Thickness can be undesirable in such flat flexible members and can in some cases pose problems for the electrical sensing operations. Increasing wire thickness can increase the cost of the device, particularly if silver or platinum wire is used.
When the tissue-engagement member is a depth electrode device, some of the problems may vary to some extent. However, the problems of time-consuming electrical hookup procedures are quite similar. Indeed, such problems are involved with electrical hookup of any plural-contact tissue-engagement member.
There is a substantial need for an improved plural-contact electrical connection device overcoming or minimizing the above problems and difficulties. In particular, there is a need for improved electrical hookup apparatus for use during placement and setup procedures involving electrical contact with brain tissue. A simple plural-contact connector which is easily usable and disposable would be highly desirable.